Gel electrolyte for lithium secondary battery and lithium secondary battery comprising same

Abstract

A gel polymer electrolyte for a lithium secondary battery and a lithium secondary battery comprising same are presented. The gel polymer electrolyte for a lithium secondary battery is a gel polymer electrolyte for a lithium secondary battery, comprising a gel polymer and a liquid electrolyte, wherein the gel polymer is: i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of a first polymerizable monomer and a second polymerizable monomer, the first polymerizable monomer being a multifunctional acrylic monomer having three or more polymerizable functional groups, and the second polymerizable monomer being one or more selected from a urethane acrylic monomer having two or more polymerizable functional groups and a polymerizable monomer including a perfluoropolyether (PFPE) unit and two or more polymerizable functional groups, and the liquid electrolyte comprises a lithium salt, an organic solvent, and acetonitrile.

Description

Gel electrolyte for lithium secondary batteries and lithium secondary batteries containing the same

[0001] The present invention relates to a gel electrolyte for a lithium secondary battery and a lithium secondary battery including the same.

[0002] Lithium secondary batteries primarily use carbon-based anode materials, such as graphite. Carbon-based anode materials exhibit no volume change during charge / discharge, contributing to the stability of lithium secondary batteries. However, their low capacity necessitates the use of higher-capacity anode materials.

[0003] Lithium metal, which has a much larger theoretical electric capacity than carbon-based negative electrode materials, can be used as a negative electrode material.

[0004] When lithium metal is charged and discharged, lithium dendrites are formed on the surface of the lithium metal due to a side reaction with the electrolyte, and the growth of the dendrites can cause a short circuit between the positive and negative electrodes, which can reduce the life characteristics of a lithium secondary battery containing lithium metal.

[0005] A method using a solid electrolyte with high modulus and high lithium ion mobility to control lithium dendrites has been proposed.

[0006] However, among solid electrolytes, polymer solid electrolytes exhibit low ionic conductivity at room temperature, making practical application difficult. In contrast, gel polymer electrolytes are easy to manufacture and exhibit excellent electrochemical performance. However, their ion transfer rates are not satisfactory, requiring further improvement.

[0007] One aspect is to provide a gel polymer electrolyte for a lithium secondary battery with improved lithium ion mobility through the polymer.

[0008] Another aspect is to provide a lithium secondary battery including the above-described gel polymer electrolyte and a method for manufacturing the same.

[0009] According to one embodiment, a gel polymer electrolyte for a lithium secondary battery comprising a gel polymer and a liquid electrolyte,

[0010] The above gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or

[0011] ii) A crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups as a first polymerizable monomer, a urethane acrylic monomer having two or more polymerizable functional groups as a first polymerizable monomer, and one or more second polymerizable monomers selected from among polymerizable monomers containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups.

[0012] The above liquid electrolyte is a gel polymer electrolyte for a lithium secondary battery containing a lithium salt, an organic solvent, and acetonitrile.

[0013] In another aspect, a lithium secondary battery comprising a negative electrode current collector, a positive electrode, and an electrolyte disposed between the positive electrode and the negative electrode is provided, wherein the electrolyte comprises the above-described gel polymer electrolyte.

[0014] According to one aspect, a gel polymer electrolyte for a lithium secondary battery containing a substance that transfers lithium cations and anions to a polymer chain to concentrate the distribution of lithium ions in a polymer chain and improve the mobility of lithium ions within the polymer chain is provided, and a lithium secondary battery using the gel polymer electrolyte having high rate characteristics and life characteristics is provided.

[0015] Figure 1 is a drawing for explaining the laminated structure of a lithium secondary battery according to an embodiment.

[0016] Figure 2 is a drawing for explaining the laminated structure of a lithium secondary battery according to another embodiment.

[0017] Figure 3 is a drawing for explaining the laminated structure of a lithium secondary battery according to another embodiment.

[0018] Figure 4 is a schematic diagram of a lithium secondary battery according to an embodiment.

[0019] Figure 5 is a schematic diagram of a lithium secondary battery according to another embodiment.

[0020] Figure 6 is a schematic diagram of a lithium secondary battery according to another embodiment.

[0021] Fig. 7 is an SEM photograph observing the lithium deposition state of a lithium secondary battery according to an embodiment.

[0022] Figure 8 is an SEM photograph observing the lithium deposition state of a lithium secondary battery according to a comparative example.

[0023] The present inventive concept described below is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present inventive concept to specific embodiments, but rather to encompass all modifications, equivalents, or alternatives within the technical scope of the present inventive concept.

[0024] The terminology used below is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. Hereinafter, the terms "comprises" or "has" and the like are intended to indicate the presence of a feature, number, step, operation, component, part, ingredient, material, or combination thereof described in the specification, but should be understood to not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, ingredients, materials, or combinations thereof. The " / " used below may be interpreted as "and" or "or" depending on the context.

[0025] In order to clearly express various layers and regions in the drawings, the thickness is shown enlarged or reduced. Similar parts are designated by the same drawing reference numerals throughout the specification. When a part such as a layer, film, region, or plate is said to be "on" or "above" another part throughout the specification, this includes not only cases where it is directly above the other part, but also cases where there is another part in between. Terms such as first, second, etc. may be used throughout the specification to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. In this specification and the drawings, components having substantially the same functional configuration are referred to by the same reference numerals, and redundant descriptions are omitted.

[0026] Unless otherwise specified herein, when a part such as a layer, film, region, or plate is said to be “on top of” another part, this includes not only cases where it is “directly on top of” the other part, but also cases where there are other parts in between.

[0027] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0028] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0029] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0030] In the present disclosure, the "particle diameter" of a particle refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter of a particle can be measured using a particle size analyzer (PSA). The "particle diameter" of a particle is, for example, the average particle diameter. The average particle diameter is, for example, the median particle diameter (D50). The median particle diameter (D50) is the size of a particle corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by, for example, laser diffraction. The average particle diameter and average major axis length of a particle can be measured using a scanning electron microscope. When the particle size is measured using a scanning electron microscope, it is determined as the average value of 30 or more randomly selected particles having a size of 1 μm or more, excluding fine particles.

[0031] In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states, and “alloy” means a mixture of two or more metals.

[0032] In the present disclosure, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation, and “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0033] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to a positive electrode active material or a negative electrode active material, and “delithiation” and “delithiating” mean a process of removing lithium from a positive electrode active material or a negative electrode active material.

[0034] In the present disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery, and “discharging” and “discharging” mean a process of removing electrochemical energy from a battery.

[0035] In the present disclosure, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during a discharge process, and “negative electrode” and “anode” mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0036] Hereinafter, a gel polymer electrolyte for a lithium secondary battery and a lithium secondary battery including the same according to exemplary embodiments will be described in more detail.

[0037] A non-cathode lithium secondary battery is a battery that uses only a cathode current collector without a cathode active material layer. When charging, lithium ions transferred from the cathode are deposited on the surface of the cathode current collector, and when discharging, the lithium deposited on the cathode current collector is eluted again and inserted into the cathode, thereby operating the battery.

[0038] Non-cathode lithium secondary batteries offer the advantage of maximizing energy density per volume / weight of the battery by omitting lithium metal, which is used as the anode active material. However, lithium metal precipitates during operation, and the uneven current concentration during oxidation / reduction causes lithium dendrites to grow. These dendrites not only cause lithium anode loss, reducing battery capacity and lifespan, but can also cause short-circuiting between the anode and cathode, posing safety concerns.

[0039] A method using a solid electrolyte with high modulus and high lithium ion mobility to control lithium dendrites has been proposed.

[0040] However, among solid electrolytes, solid polymer electrolytes have low ionic conductivity at room temperature, and solid ceramic electrolytes are difficult to manufacture and handle, making practical application difficult. In contrast, gel polymer electrolytes are easy to manufacture and exhibit excellent electrochemical performance. However, their insufficient lithium ion transfer rate leads to poor rate characteristics and even failure to operate at room temperature, necessitating further improvement.

[0041] Accordingly, in order to solve the above-described problem, the present disclosure provides a gel polymer electrolyte for a lithium secondary battery containing a material that transfers lithium cations and anions to a polymer chain, thereby concentrating the distribution and movement of lithium ions in the polymer chain and improving the mobility of lithium ions within the polymer chain.

[0042] According to one embodiment, a gel polymer electrolyte for a lithium secondary battery comprises a gel polymer and a liquid electrolyte, wherein the gel polymer is a crosslinked product of i) a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of a first polymerizable monomer which is a multifunctional acrylic monomer having three or more polymerizable functional groups and a second polymerizable monomer which is at least one selected from a urethane acrylic monomer having two or more polymerizable functional groups and a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups, and the liquid electrolyte may include a lithium salt, an organic solvent, and acetonitrile.

[0043] In a gel polymer electrolyte according to one embodiment, acetonitrile plays a role in concentrating the distribution of lithium ions in the polymer chain by transferring anions along with lithium cations to the polymer chain. Acetonitrile is a neutral molecule with improved anion interaction in addition to lithium cation interaction, and by using a gel polymer electrolyte formed using a liquid electrolyte containing such acetonitrile, a lithium secondary battery with improved capacity and long life and reduced resistance can be provided.

[0044] According to one embodiment, the content of the acetonitrile is 2 wt% to 30 wt%, 3 wt% to 20 wt%, or 3 wt% to 10 wt% based on 100 wt% of the total weight of the electrolyte. When the content of the acetonitrile is within the above range, the interaction with lithium cations and anions is excellent, thereby forming a gel polymer electrolyte with improved lithium ion mobility.

[0045] In a lithium secondary battery according to an embodiment, acetonitrile can effectively prevent the formation of lithium dendrite by transferring lithium ions to a polymer chain, thereby ensuring that lithium ions are transferred only through the polymer chain, thereby uniformly transferring lithium ions onto the negative electrode.

[0046] If acetonitrile is not added to the gel polymer electrolyte according to the embodiment, lithium ions are transferred not only through the polymer chain but also through the liquid electrolyte, and lithium ions are partially concentrated, and lithium dendrite may be formed.

[0047] According to one embodiment, the organic solvent includes a carbonate-based compound, and the carbonate-based compound may include fluoroethylene carbonate (FEC) and diethyl carbonate (DEC). For example, the content of the carbonate-based compound may be 5 to 45 wt% with respect to the total weight of the liquid electrolyte. For example, the content of the carbonate-based compound may be 10 to 45 wt%, 15 to 45 wt%, 20 to 45 wt%, or 20 to 40 wt% with respect to the total weight of the liquid electrolyte.

[0048] According to one embodiment, the mixing weight ratio of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) among the carbonate compounds may be 1:10 to 1:1, 1:8 to 1:1, 1:5 to 1:1, or 1:3 to 1:1.

[0049] According to one embodiment, a gel polymer electrolyte can be formed in a semi-solid state by confining a liquid in a polymer matrix obtained by polymerization. At this time, when a gel polymer electrolyte is manufactured using a monomer having a strong affinity for lithium ions and a monomer having a strong affinity for anions as a polymerizable monomer (crosslinking monomer) for manufacturing the polymer matrix, the distribution of lithium ions and anions is concentrated in the polymer chain, and low-molecular-weight liquid molecules assist the movement between ion bonding sites in the polymer chain, so that the overall lithium movement does not proceed separately in two phases, a liquid phase and a polymer phase, but lithium ions move through the polymer chain, so that lithium is uniformly deposited on the negative electrode current collector, and lithium can be transferred to a uniform concentration on the negative electrode current collector without increasing dendritic lithium precipitation and be uniformly deposited.

[0050] The multifunctional acrylic monomer having three or more polymerizable functional groups, the first polymerizable monomer, and the second polymerizable monomer have strong affinity for lithium cations and anions, so that the gel polymer electrolyte obtained from them can facilitate the movement of lithium ions through the polymer chain. Therefore, by using such a gel polymer electrolyte, a lithium secondary battery with improved life characteristics can be manufactured. Here, the lithium cations and anions are derived from a lithium salt, and for example, when LiPF6 is used as the lithium salt, the anion is, for example, PF6. - can be heard.

[0051] A gel polymer electrolyte according to an embodiment can be prepared using a composition for forming a gel polymer electrolyte. The composition for forming a gel polymer electrolyte contains a polymerizable monomer for forming a gel polymer, a liquid electrolyte, and an initiator.

[0052] For example, the initiator may include benzoyl peroxide, di-tert-butyl peroxide, dibenzoyl peroxide, azobisdisobutyronitrile, 1,1'-azodi(hexahydrobenzonitrile), 2,2'-azodi(2-methylbutyronitrile), or any combination thereof.

[0053] When a gel polymer electrolyte is formed using a liquid electrolyte containing a polymerizable monomer and acetonitrile according to an embodiment, lithium ions move and exist in large numbers around the gel polymer formed from the polymerizable monomer, thereby increasing the lithium transport rate. In addition, lithium ions are uniformly arranged on the negative electrode, effectively preventing the formation of lithium dendrites.

[0054] The multifunctional acrylic monomer having three or more polymerizable functional groups and the multifunctional acrylic monomer containing a urethane group have strong lithium cation (Li+) interaction and anion interaction, so that lithium cation ions are transferred through the polymer chain and anions are trapped, thereby greatly increasing the lithium cation transport rate (Li+ transferenece number). Here, the lithium cation and anion are, for example, the cation and anion of a lithium salt, and when LiPF6 is used as the lithium salt, the anion is, for example, PF6 - am.

[0055] A gel polymer electrolyte for a lithium secondary battery according to one embodiment is a gel polymer electrolyte for a lithium secondary battery, comprising a gel polymer and a liquid electrolyte, wherein the gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of at least one second polymerizable monomer selected from a multifunctional acrylic monomer having three or more polymerizable functional groups, which is a first polymerizable monomer, and a urethane acrylic monomer having two or more polymerizable functional groups, and a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups. And the liquid electrolyte includes a lithium salt, an organic solvent, and acetonitrile.

[0056] The above gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of a first polymerizable monomer which is a multifunctional acrylic monomer having three or more polymerizable functional groups and a second polymerizable monomer which is at least one selected from a urethane acrylic monomer having two or more polymerizable functional groups and a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups.

[0057] A multifunctional acrylic monomer having three or more polymerizable functional groups has, for example, three or more polymerizable functional groups, for example, three to six polymerizable functional groups. When the multifunctional acrylic first polymerizable monomer has three or more polymerizable functional groups, a gel polymer electrolyte having excellent physical properties can be obtained. These polymerizable monomers include, for example, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate (TMPTMA), propoxylated (3) trimethylolpropane triacrylate (PO(3)TMPTA), propoxylated (6) trimethylolpropane triacrylate (PO(6)TMPTA), ethoxylated trimethylolpropane triacrylate, di(trimethylolpropane) tetraacrylate (Di(trimethylolpropane) tetraacrylate), pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), dipentaerythritol pentaacrylate (DPEPA), dipentaerythritol It may be hexaacrylate (DPHA) or a combination thereof.

[0058] According to one embodiment, the urethane acrylic monomer having two or more functional groups may include two or more units represented by the following chemical formula 1.

[0059] <Chemical Formula 1>

[0060]

[0061] In the above chemical formula 1,

[0062] * is a bonding site with an adjacent atom.

[0063] According to one embodiment, the urethane acrylic monomer having two or more functional groups may include the following compound 1.

[0064] Compound 1

[0065]

[0066] In the above compound 1, n is an integer from 1 to 100, EG represents an ethylene group, DEG represents diethylene glycol, and TMP represents trimethylolpropane.

[0067] For example, since a urethane acrylic monomer having two or more functional groups has high mechanical strength and elasticity by including a urethane moiety, when it is used as a second polymerizable monomer to form a crosslinked product with the first polymerizable monomer, a gel polymer electrolyte having high mechanical strength and elasticity can be manufactured.

[0068] As a second polymerizable monomer, other monomers containing a polyfunctional functional group having a similar structure to the polyfunctional acrylic monomer containing a urethane group may be additionally mixed and used. As the other monomers containing such a polyfunctional functional group, for example, one or more selected from the group consisting of urethane acrylate methacrylate, urethane epoxy methacrylate, and Arkema's product names Satomer N3DE180 and N3DF230 may be used.

[0069] When a polyfunctional acrylic monomer containing a urethane group is used as a polymerizable monomer, it can act as a diluent in the electrolyte, thereby reducing the viscosity of the composition for forming a gel polymer electrolyte. The viscosity of the composition for forming a gel polymer electrolyte can be 4 to 10 cps. Therefore, using a composition having such a viscosity can facilitate injection into a battery structure.

[0070] According to one embodiment, the polymerizable monomer containing the perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups may include a unit represented by the following chemical formula 2 and two or more units represented by the following chemical formula 3.

[0071] <Chemical Formula 2>

[0072]

[0073] In chemical formula 2,

[0074] * and *' are the bonding sites with adjacent atoms, respectively,

[0075] m and n are greater than 0, and the sum of m+n is in the range of 2 to 300,

[0076] <Chemical Formula 3>

[0077]

[0078] In the above chemical formula 3,

[0079] R1 is hydrogen or a C1-C6 alkyl group, and * is a bonding site with an adjacent atom.

[0080] According to one embodiment, the polymerizable monomer containing the PFPE unit and having two or more polymerizable functional groups contains a perfluoroether unit and thus has excellent ionic conductivity, and may include, for example, a compound represented by the following chemical formula 4.

[0081] <Chemical Formula 4>

[0082]

[0083] In chemical formula 4, R1 is hydrogen or a C1-C6 alkyl group, m and n are greater than 0, and the sum of m+n is in the range of 2 to 300 or in the range of 1 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100.

[0084] In the above chemical formula 4, the wavy line may represent any linker group.

[0085] The weight average molecular weight of the compound represented by the above chemical formula 4 is 400 to 10,000, 400 to 5,000, or 500 to 3,000.

[0086] In the polymerizable monomer containing the above PFPE unit and having two or more polymerizable functional groups, the number of polymerizable functional groups may be three or more, or four or more. The compound of the above chemical formula 3 has four (meth)acrylic groups, which are crosslinking functional groups, and thus can form a network capable of trapping a large amount of liquid while using a small amount compared to a case where a compound having a small number of crosslinking functional groups is used.

[0087] The above second polymerizable monomer is a compound represented by the following chemical formula 4-1, a compound represented by the following chemical formula 4-2, or a combination thereof.

[0088] <Chemical Formula 4-1>

[0089]

[0090] In Chemical Formula 4-1, m and n are greater than 0, and the sum of m+n is in the range of 2 to 300 or in the range of 1 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100. In Chemical Formula 4-1, the wavy line may represent any linker group.

[0091] <Chemical Formula 4-2>

[0092]

[0093] In Chemical Formula 4-2, m and n are greater than 0, and the sum of m+n is in the range of 2 to 300 or in the range of 1 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100. In Chemical Formula 4-2, the wavy line may represent any linker group.

[0094] A polymerizable monomer containing the above PFPE unit and having two or more polymerizable functional groups is commercially available under the trade name Fluorolink. ® AD 1700 PFPE - commercially available as perfluoropolyether (PFPE) urethane acrylate (PFPE backbone, Mw = 1500) (Solvay Specialty Polymers Italy SpA).

[0095] <AD 1700>

[0096]

[0097] The mixing weight ratio of the first polymerizable monomer, which is a multifunctional acrylic monomer, and at least one second polymerizable monomer selected from a urethane acrylic monomer having two or more functional groups and a polymerizable monomer containing a PFPE unit and having two or more polymerizable functional groups is in the range of 1:10 to 10:1. The weight ratio of the first polymerizable monomer and the second polymerizable monomer is, for example, 5:1 to 1:1 or 3:1 to 1:1. When the weight ratio of the first polymerizable monomer and the second polymerizable monomer is in the above range, a gel polymer electrolyte with improved ionic conductivity and physical properties can be formed.

[0098] The gel polymer electrolyte made of a crosslinked product obtained from the first polymerizable monomer and the second polymerizable monomer is Li + Cations such as and PF6 - The interaction with anions such as is very strong. This strong interaction can be confirmed to be caused by the difference in electron density distribution in the DFT simulation.

[0099] According to one embodiment, the content of the liquid electrolyte may be 88 to 99 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte, and the content of the gel polymer may be 1 to 10 parts by weight. For example, the content of the liquid electrolyte may be 88 to 98 parts by weight, 90 to 98 parts by weight, 92 to 98 parts by weight, or 94 to 98 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte.

[0100] For example, the content of the gel polymer may be 2 to 12 parts by weight, 2 to 10 parts by weight, 2 to 8 parts by weight, or 2 to 6 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte.

[0101] The above gel polymer electrolyte-containing separator is manufactured separately in the form of a self-supporting membrane, and a lithium secondary battery can be manufactured by positioning the gel polymer electrolyte-containing separator on top of the negative electrode current collector and protective film and placing the positive electrode on top of it.

[0102] Alternatively, a lithium secondary battery having a separator containing a gel polymer electrolyte can be manufactured by forming a battery structure by positioning a negative electrode current collector and a protective film, and arranging a separator and a positive electrode on top of the battery structure, and injecting a composition for forming a gel polymer electrolyte into the battery structure and performing heat treatment.

[0103] A lithium secondary battery according to an embodiment includes: a negative electrode current collector; a protective film formed on the negative electrode current collector; a separator; a gel polymer electrolyte; and a positive electrode, and includes a negative electrode active material layer disposed between the negative electrode current collector and the protective film, or the negative electrode active material layer is absent (free), the protective film includes boron nitride (BN) and a binder, and the gel polymer electrolyte contains a gel polymer, boron nitride (BN), acetonitrile, and a liquid electrolyte.

[0104] In a lithium secondary battery according to an embodiment, the thickness of the protective film is 1 to 10 um and the thickness of the separator is 5 to 20 um. When the thickness of the protective film and the separator are within the above ranges, a lithium secondary battery having improved ionic conductivity and physical properties and improved lifespan characteristics can be provided.

[0105] In the above gel polymer electrolyte, the liquid electrolyte contains an organic solvent, which acts as a medium through which ions involved in the electrochemical reaction of the battery can move. The organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0106] Examples of the above carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0107] Ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0108] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. In addition, examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol, and examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0109] The above organic solvents can be used alone or in combination of two or more.

[0110] In addition, when using a carbonate solvent, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0111] According to one embodiment, the carbonate compound includes fluoroethylene carbonate (FEC) and diethyl carbonate (DEC), and the mixing weight ratio of the FEC and DEC is 1:10 to 1:1.

[0112] The lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes. Lithium difluorobis(oxalato)phosphate (LiDFOB) and LiBF4 are used as the lithium salt. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M, 0.2 M to 4.0 M, or 0.3 M to 4.0 M.

[0113] According to one embodiment, the lithium salt may include lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF4).

[0114] According to one embodiment, the mixing weight ratio of lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF4) may be 1:2 to 1:0.3.

[0115] According to one embodiment, the lithium salt is LiPF6, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium bis(oxalato)borate (LiBOB) may further include one or more selected from the group consisting of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, and lithium bis(oxalato)borate. The concentration of the lithium salt may be, for example, from 0.1 M to 5.0 M.

[0116] The gel polymer electrolyte may be present within the separator and at the interface between the separator and the positive electrode. The gel polymer electrolyte may be contained within a portion of the positive electrode.

[0117] Figure 1 shows a laminated structure of a lithium secondary battery according to an embodiment.

[0118] A lithium secondary battery (1) has a negative electrode (20) including a negative electrode current collector (21), and a negative electrode active material layer is absent.

[0119] A protective film (22) can be optionally formed between the negative electrode current collector (21) and the separator (30).

[0120] A positive electrode (10) is sequentially arranged on top of the above separator (30). The positive electrode (10) contains a positive electrode active material layer (12) and a positive electrode current collector (11). A gel polymer electrolyte is contained within the separator (30).

[0121] As shown in Fig. 2, a gel polymer electrolyte (31) can be placed between the separator (30) and the anode (10). Although not shown in Figs. 1 and 2, the gel polymer electrolyte can be contained in the anode (10).

[0122] Between the negative electrode current collector (21) and the protective film (22), a negative electrode active material layer (23) may be further disposed as shown in Fig. 3. The negative electrode active material layer may include lithium metal or a lithium alloy.

[0123] A lithium deposition layer may further be included between the negative electrode current collector (21) and the protective film (22).

[0124] The protective film is a lithium-ion conductive buffer layer that prevents the separator containing the gel polymer electrolyte from contacting lithium metal. It also inhibits the formation and growth of lithium dendrites on the negative electrode current collector.

[0125] According to another embodiment, a lithium electrodeposition induction layer may be further included between the negative electrode current collector and the protective film.

[0126] In a lithium secondary battery according to an embodiment, the thickness expansion rate of the negative electrode, expressed by the following mathematical formula 1, is 150% or less.

[0127] <Formula 1>

[0128] Thickness expansion rate of the negative electrode (%) = [thickness of the lithium precipitation layer formed on the negative electrode current collector after 100 cycles of charging / thickness of the lithium precipitation layer formed on the negative electrode current collector after formation] Х100

[0129] For example, the thickness expansion ratio of the negative electrode may be 140% or less, 139% or less, 138% or less, 136% or less, 105 to 136%, or 110 to 136%. By including a binder including a crosslinked polymer with increased modulus, the strength of the binder is increased, thereby suppressing volume changes of the negative electrode during charge and discharge. Charge and discharge conditions may refer to the evaluation examples.

[0130] The binder of the protective film can be, for example, vinylidenefluoride-hexafluoropropylene (VDF-HFP) copolymer, polyethylene oxide, polypropylene oxide, polydimethylsiloxane, polyacrylonitrile, polymethyl(meth)acrylate, polyvinyl chloride, polyvinylidene fluoride, polyvinylidenefluoride-co-hexafluoropropylene, polyethyleneimine, polyphenylene terephthalamide, polymethoxypolyethyleneglycol(meth)acrylate, poly2-methoxy ethylglycidyl ether, or a combination thereof.

[0131] The binder of the above protective film may include, for example, a crosslinked polymer of a first polymer and a second polymer, wherein the first polymer containing a hydroxyl group and the second polymer having a crosslinkable functional group are crosslinking reaction products.

[0132] The weight ratio of the first polymer and the second polymer is 50:50 to 99:1, and the second polymer is at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0133] The protective film is dense, increasing its density and strength, allowing free lithium ion movement and enhancing lithium ion transport, thereby improving lithium electrodeposition characteristics. Consequently, ionic conductivity is improved, thereby enhancing the high-rate characteristics of lithium secondary batteries. Furthermore, by positioning the protective film over the negative electrode active material layer, it effectively blocks and suppresses side reactions between the negative electrode active material layer and the electrolyte.

[0134] The protective film may further comprise an inorganic material. The inorganic material is selected from the group consisting of silica (SiO2), alumina (Al2O3), titanium oxide (TiO2), lithium titanium oxide (LiTiO2), barium titanium oxide (BaTiO2), lithium alumina (LiAlO2), and zeolite, or a mixture thereof.

[0135] The mixing weight ratio of the first polymer containing a hydroxyl group and the second polymer is adjusted to be in the range of 50:50 to 99:1, 50:50 to 90:10, or 60:40 to 90:10.

[0136] When a protective film according to an embodiment of the present invention is present on the surface of a negative electrode active material layer including lithium metal, the generation and / or growth of lithium dendrites on the negative electrode current collector can be effectively prevented. In addition, the cycle characteristics and stability of a negative electrode including the above-described protective film and a lithium secondary battery employing the same are improved.

[0137] The above hydroxyl group-containing first polymer is carboxymethyl cellulose (CMC); polyvinyl alcohol (PVA); Vinyl acetate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, acrylic acid, methacrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, itaconic acid, maleic acid, 2-isocyanatoethyl (meth)acrylate, 3-isocyanatopropyl (meth)acrylate, A polymerization reaction product of one or more monomers selected from among 4-isocyanatobutyl (meth)acrylate, (meth)acrylamide, ethylene di(meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol di(meth)acrylate, trimethylene propane tri(meth)acrylate, trimethylene propane triacrylate, 1,3-butanediol (meth)acrylate, 1,6-hexanediol di(meth)acrylate, allyl acrylate, and N-vinyl caprolactam, or a hydrolyzate thereof, may be mentioned.

[0138] The first polymer may be polyvinyl alcohol (PVA). For example, polyvinyl alcohol may be a hydrolyzate obtained by hydrolyzing polyvinyl acetate with an alkali.

[0139] The degree of saponification of the polyvinyl alcohol may be 60 to 99%, 70 to 95%, 75 to 90%, or 80 to 90%. For example, the degree of saponification of the polyvinyl alcohol may be 85 to 90%. In the above saponification range, the physical properties due to the protective film may be further improved. The weight average molecular weight of the first polymer may be 10,000 to 500,000 Dalton, 10,000 to

[0140] It may be 500,000 Dalton, 10,000 to 400,000 Dalton, 10,000 to 300,000 Dalton, 10,000 to 200,000 Dalton, 50,000 to 150,000 Dalton, 70,000 to 100,000 Dalton, or 80,000 to 100,000 Dalton. The properties of the protective film may be further improved within the weight average molecular weight range of the first polymer.

[0141] The above protective film may further include a second polymer having a functional group capable of crosslinking with the first polymer containing a hydroxyl group. In this case, the protective film further includes a crosslinked polymer of the first polymer and the second polymer.

[0142] The second polymer comprises at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0143] The above fluorinated polyamic acid may be, for example, a polymer represented by the following chemical formula 5 or 6, and the above fluorinated polyimide may be a polymer represented by the following chemical formula 7 or 8.

[0144] [Chemical Formula 5]

[0145]

[0146] [Chemical Formula 6]

[0147]

[0148] [Chemical Formula 7]

[0149]

[0150] [Chemical Formula 8]

[0151]

[0152] In the above formulas, M is an alkali metal,

[0153] Ar1 and Ar3 are independently an aromatic ring group selected from a substituted or unsubstituted tetravalent arylene group having 6 to 24 carbon atoms or a substituted or unsubstituted tetravalent heteroarylene group having 4 to 24 carbon atoms, wherein the aromatic ring group is one aromatic ring, a ring in which two or more aromatic rings are fused, or two or more aromatic rings are single bonded, -O-, -S-, -C(=O)-, -S(=O)2-, -Si(R a )(R b )-(R a and R b are independently a C1-C10 alkyl group), a substituted or unsubstituted C1-C10 alkylene group, or a ring connected by -C(=O)-NH-,

[0154] Ar2 and Ar4 are independently an aromatic ring group selected from a substituted or unsubstituted divalent arylene group having 6 to 24 carbon atoms or a substituted or unsubstituted divalent heteroarylene group having 4 to 24 carbon atoms, wherein the aromatic ring group is one aromatic ring, a ring in which two or more aromatic rings are fused, a ring in which two or more aromatic rings are single bonded, -O-, -S-, -C(=O)-, -S(=O)2-, -Si(R a )(R b )-(R a and R b are independently a C1-C10 alkyl group), a substituted or unsubstituted C1-C10 alkylene group, or a ring connected by -C(=O)-NH-,

[0155] At least one of Ar1 to Ar4 is substituted with a halogen group,

[0156] X1 is the first functional group, which is -COOH, -OH, -CO-NH2, or -COH,

[0157] n and m are the mole fractions within the repeating unit, respectively, and 0 <n≤1, 0≤m<1, n+m=1이다.

[0158] The halogen group may be a fluorine group, a chlorine group, a bromine group, or an iodine group. For example, the halogen group may be a fluorine group.

[0159] Here, Ar1 and Ar3 are independently selected from the following chemical formulae 5a and 5b, and Ar2 and Ar4 can be independently selected from the following chemical formulae 5c to 5e.

[0160] there is.

[0161] [Chemical Formula 5a] [Chemical Formula 5b] [Chemical Formula 5c]

[0162]

[0163] [Chemical Formula 5d] [Chemical Formula 5e]

[0164]

[0165] In the above chemical formulas 5a to 5e, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 and R 16 are each independently hydrogen, halogen, -COOH, -OH, -CO-NH2, -COH, a halogen-substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a halogen-substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a halogen-substituted or unsubstituted heteroaryl group having 2 to 20 carbon atoms; provided that R1 to R 16At least one of which is a halogen group or a group substituted with a halogen group; A1, A2 and A3 are each independently a single bond, -O-, -C(=O)-, -S-, -S(=O)2-, -Si(Ra)(Rb)- (Ra and Rb are each independently an alkyl group having 1 to 10 carbon atoms), an alkylene group having 1 to 10 carbon atoms substituted or unsubstituted with a halogen, or -C(=O)-NH-; provided that the above chemical formulas 5c to 5e, which become Ar2, are R5 to R 16 At least one of the first functional groups is -COOH, -OH, -CO-NH2, or -COH.

[0166] For example, in the above chemical formulas 5a to 5e, R1 to R 16 are each independently a hydrogen atom, a halogen atom, a hydroxyl group, -CH3, or -CF3, provided that the above chemical formulas 5c to 5e, which become Ar2, are R5 to R 16 At least one of the first functional groups is -COOH, -OH, -CO-NH2, or -COH; A2 and A3 can each independently be a single bond, -O-, -CO-, -S-, -SO2-, -C(CH3)2-, -CONH-, -C(CF3)2-, -CH2-, or -CF2-.

[0167] The above polyamic acid may be, for example, a polymer represented by the following chemical formula 9 or 10, and the above polyimide may be a polymer represented by the following chemical formula 11 or 12.

[0168] [Chemical Formula 9]

[0169]

[0170] [Chemical Formula 10]

[0171]

[0172] [Chemical Formula 11]

[0173]

[0174] [Chemical Formula 12]

[0175]

[0176] In the above chemical formulas 9 to 12, M is lithium or sodium,

[0177] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , and R 12 are independently hydrogen, halogen, -COOH, -OH, -CO-NH2, -COH, an alkyl group having 1 to 10 carbon atoms substituted or unsubstituted with a halogen, an aryl group having 6 to 20 carbon atoms substituted or unsubstituted with a halogen, or a heteroaryl group having 2 to 20 carbon atoms substituted or unsubstituted with a halogen, provided that R1 to R 12 At least one of which is a halogen group or a group substituted with a halogen group,

[0178] A1 and A2 are each independently a single bond, -O-, -S-, -C(=O)-, -S(=O)2-, -Si(Ra)(Rb)- (Ra and Rb are each independently an alkyl group having 1 to 10 carbon atoms), an alkylene group having 1 to 10 carbon atoms which is unsubstituted or substituted with halogen, or -C(=O)-NH-;

[0179] However, at least one of R5, R6, R7, and R8 is -COOH, -OH, -CO-NH2, or -COH, and n and m are each a mole fraction within the repeating unit, 0 <n≤1, 0≤m<1, n+m=1이다.

[0180] The halogen group may be a fluorine group, a chlorine group, a bromine group, or an iodine group. For example, the halogen group may be a fluorine group. Here, Ar1 and Ar3 may be independently selected from the chemical formulae 5a and 5b, and Ar2 and Ar4 may be independently selected from the chemical formulae 5c to 5e.

[0181] The above polyamic acid is represented by the following chemical formula 13 or 14, and the above polyimide is a polymer represented by the following chemical formula 15 or 16.

[0182] [Chemical Formula 13]

[0183]

[0184] [Chemical Formula 14]

[0185]

[0186] [Chemical Formula 15]

[0187]

[0188] [Chemical Formula 16]

[0189]

[0190] In the above chemical formulas 13 to 16, n and m are each a mole fraction within a repeating unit, and 0 <n≤1, 0≤m<1, n+m=1이다.

[0191] For example, in the second polymer, the mole fractions of repeating units containing a crosslinking group and repeating units not containing a crosslinking group are each 0. <n≤0.5, 0.5≤m<1 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.1≤n≤0.4, 0.6≤m≤0.9 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.15≤n≤0.35, 0.65≤m≤0.85 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.2≤n≤0.3, 0.7≤m≤0.8 및 n+m=1일 수 있다. 상기 몰분율 범위에서 더욱 향상된 물성을 제공할 수 있다.

[0192] For example, the second polymer may be a random copolymer. For example, the second polymer may be a block copolymer.

[0193] The weight average molecular weight of the second polymer may be 10,000 to 1,200,000 Dalton, 10,000 to 1,100,000 Dalton, 10,000 to 1,000,000 Dalton, 10,000 to 500,000 Dalton, 100,000 to 500,000 Dalton, 100,000 to 400,000 Dalton, for example, 100,000 to 300,000 Dalton. The properties of the protective film may be further improved within the weight average molecular weight range of the first polymer.

[0194] In the above protective film, the weight ratio of the first polymer and the second polymer containing a hydroxyl group included in the third polymer may be 99:1 to 50:50, 95:5 to 55:45, 95:5 to 60:40, 95:5 to 65:35, or 90:10 to 70:30. The physical properties of the protective film may be further improved within the weight ratio range of the first polymer to the second polymer.

[0195] The hydroxyl groups of the first polymer and the carboxyl groups of the second polymer react with each other to form an ester bond, thereby forming a third polymer crosslinked with the first and second polymers. The formation of the third polymer enhances the stability of the protective film, and in the case of halogen groups such as fluorine functional groups, it can improve interfacial stability by reducing the formation of irreversible lithium inclusions.

[0196] The protective film according to an embodiment of the present invention comprises a crosslinked polymer of polyvinyl alcohol and polyamic acid. The polyamic acid is, for example, a polymer represented by the chemical formula 13 or 14 described above.

[0197] In another embodiment, the crosslinked polymer of the protective film is a crosslinked polymer of polyvinyl alcohol and fluorinated polyimide (PVA / PI-f). The fluorinated polyimide is a polymer represented by the chemical formula 15 or 16 described above.

[0198] The above protective film may contain a polar functional group as a binder and may be free of lithium salt.

[0199] The protective film may further contain a lithium salt, and when containing a lithium salt, excellent ionic conductivity of the protective film can be secured. The lithium salt may be one or more of materials such as LiSCN, LiN(CN)2, LiClO4, LiBF4, LiAsF6, LiPF6, LiCF3SO3, LiC(CF3SO2)3, LiC(FSO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, and LiB(C2O4)2.

[0200] In the negative electrode according to an embodiment, the negative electrode active material layer includes lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, or a combination thereof, wherein the lithium alloy contains lithium and a first metal.

[0201] The negative electrode active material layer contains a carbon-based compound; a mixture of at least one selected from a carbon-based material and a first metal; a composite of at least one selected from a carbon-based material and a first metal; or a combination thereof, wherein the carbon-based material includes amorphous carbon, and the average particle size of the amorphous carbon is from 10 nm to 100 nm. The carbon-based material includes carbon black, carbon nanotubes, carbon nanofibers, fullerenes, activated carbon, carbon fibers, or a combination thereof.

[0202] The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0203] A lithium metal layer may be further disposed between the negative electrode current collector and one surface of the protective film.

[0204] There is. A lithium metal layer can be further disposed on the other surface opposite to the above-mentioned one surface of the above-mentioned protective film.

[0205] The thickness of the protective film is 1 to 10 μm, 1 to 8 μm, 1 to 7 μm, 2 to 6 μm, or 3 to 5 μm. When the thickness of the protective film is within the above range, the internal resistance increases, and the energy density of the lithium battery is not reduced, and the energy density is excellent and the high-rate characteristics and life characteristics are improved.

[0206] According to another aspect, a lithium secondary battery is provided, comprising: a positive electrode; a negative electrode according to an embodiment; and an electrolyte disposed between the positive electrode and the negative electrode, wherein the electrolyte comprises the gel polymer electrolyte for a lithium secondary battery as described above.

[0207] According to one embodiment, the electrolyte may further include a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0208] For example, the organic electrolyte can be manufactured by dissolving a lithium salt in an organic solvent.

[0209] For example, the solid electrolyte may include an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof. A gel electrolyte may have a gel state, for example, without including a polymer.

[0210] For example, the gel electrolyte may include a polymer gel electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode active material layer, and at least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, wherein the base film includes a polymer, and the polymer includes polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof, and the metal layer includes indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0211] The lithium metal may include, for example, a lithium metal foil, a lithium alloy foil, or a combination thereof. The lithium powder may include, for example, a lithium metal powder, a lithium alloy powder, or a combination thereof. A lithium alloy is an alloy of lithium and another metal that can be alloyed with lithium, such as a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, or a lithium-tin alloy. The negative electrode active material layer including a lithium metal foil may be, for example, a lithium metal layer. The negative electrode active material layer including a lithium alloy foil may be, for example, a lithium alloy layer. The negative electrode active material layer including a lithium metal powder and / or a lithium alloy powder may be introduced by coating a slurry including lithium powder and a binder onto a negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer may be formed of a metal-based negative electrode active material.

[0212] The thickness of the lithium metal may be, for example, 1 μm to 50 μm, 1 μm to 30 μm, or 10 μm to 30 μm, or 10 μm to 80 μm. When the lithium metal has a thickness in this range, the life characteristics of the lithium battery including the protective film can be further improved. The particle size of the lithium powder may be, for example, 0.1 μm to 3 μm, 0.1 μm to 2 μm, or 0.1 μm to 2 μm. When the lithium powder has a thickness in this range, the life characteristics of the lithium battery including the protective film can be further improved.

[0213] The thickness of the negative electrode active material layer may be, for example, 0.1 ㎛ to 500 ㎛, 1 ㎛ to 500 ㎛, or 10 ㎛ to 500 ㎛, but is not necessarily limited to this range and may be adjusted according to the shape, capacity, etc. of the required lithium secondary battery. When the thickness of the negative electrode active material layer is within the above range, the cycle characteristics are improved without lowering the energy density of the lithium secondary battery.

[0214] A lithium secondary battery according to an embodiment does not include a negative electrode active material layer disposed between a negative electrode current collector (21) and a protective film (22). An anode not including a negative electrode active material layer may include a negative electrode active material layer by plating lithium metal between the negative electrode current collector (21) and the protective film (22) upon charging after being introduced into a lithium battery together with a positive electrode and an electrolyte. The negative electrode active material layer may be a lithium plating layer (plated lithium layer).

[0215] Lithium secondary batteries may further include a separator.

[0216] The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness can generally be 5 to 20 μm. Examples of such separators include sheets or non-woven fabrics made of olefin-based polymers such as polypropylene, glass fibers, or polyethylene. When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte may also function as the separator.

[0217] Among the above separation membranes, specific examples of olefin-based polymers include polyethylene, polypropylene, or a multilayer membrane of two or more layers thereof, and mixed multilayer membranes such as a polyethylene / polypropylene two-layer separation membrane, a polyethylene / polypropylene / polyethylene three-layer separation membrane, and a polypropylene / polyethylene / polypropylene three-layer separation membrane may be used.

[0218] In a lithium secondary battery according to an embodiment, the liquid electrolyte contains a lithium salt and an organic solvent.

[0219] As the organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, ethyl propionate, etc. can be used. Carbonate solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, and diethyl carbonate can be used.

[0220] The above lithium salt can be any one that is commonly used in lithium secondary batteries, and as a material that is easily dissolved in the non-aqueous solvent, for example, one or more of the following materials can be used: LiSCN, LiN(CN)2, LiClO4, LiBF4, LiAsF6, LiPF6, LiCF3SO3, LiC(CF3SO2)3, LiC(FSO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, and LiB(C2O4)2.

[0221] The concentration of the lithium salt may be, for example, 1 to 5 M, for example, 1 to 2.5 M, in the liquid electrolyte. In the above range, a sufficient amount of lithium ions required for charging and discharging a lithium secondary battery can be generated.

[0222] When a gel-type polymer electrolyte exists in the pores of a porous substrate, the interfacial resistance between the positive electrode, negative electrode, and separator is minimized, and lithium movement becomes easier.

[0223] According to one embodiment, the negative electrode active material layer may be arranged during the assembly of the lithium secondary battery. According to another embodiment, the negative electrode active material layer may include a negative electrode active material layer by plating lithium metal after charging. The negative electrode active material layer may be a lithium plating layer (plated lithium layer).

[0224] The above negative electrode active material layer includes lithium metal or a lithium alloy.

[0225] When the negative electrode active material layer is placed at the time of assembly, it may include only a carbon-based material, a carbon-based material, and at least one selected from metals and metalloids.

[0226] The carbon-based material includes amorphous carbon, and the average particle diameter of the amorphous carbon is 10 nm to 100 nm, and the carbon-based material includes carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, or a combination thereof.

[0227] The above negative active material layer includes a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof, wherein the lithium alloy contains lithium and a first metal.

[0228] The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0229] The negative electrode active material layer (22) may include, for example, lithium foil, lithium powder, or a combination thereof. The lithium foil may include, for example, lithium metal foil, lithium alloy foil, or a combination thereof. The lithium powder may include lithium metal powder, lithium alloy powder, or a combination thereof. A lithium alloy is an alloy of lithium and another metal that can be alloyed with lithium, such as a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, or a lithium-tin alloy. The negative electrode active material layer including a lithium metal foil may be, for example, a lithium metal layer. The negative electrode active material layer including a lithium alloy foil may be, for example, a lithium alloy layer. The negative electrode active material layer including a lithium metal powder and / or a lithium alloy powder may be introduced by coating a slurry including lithium powder and a binder, etc., on a negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer can be made of a metal-based negative electrode active material.

[0230] The negative electrode current collector is composed of a material that does not react with lithium, i.e., does not form an alloy or compound. The material constituting the negative electrode current collector includes, but is not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material that is used as an electrode current collector in the relevant technical field may be used. The negative electrode current collector may be composed of one of the above-mentioned metals, or may be composed of an alloy or a coating material of two or more metals. The negative electrode current collector is, for example, in the form of a plate or foil.

[0231] In one embodiment of the present invention, the positive electrode collector uses a plate or foil made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The thickness of the positive electrode collector is, for example, 1 µm to 100 µm, 1 µm to 50 µm, 5 µm to 25 µm, or 10 µm to 20 µm.

[0232] The negative electrode active material layer may contain a negative electrode active material and a binder.

[0233] The negative active material has, for example, a particle form. The average particle diameter of the negative active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 100 nm, or 20 nm to 80 nm. When the negative active material has an average particle diameter in this range, reversible plating and / or dissolution of lithium can be facilitated during charge and discharge. The average particle diameter of the negative active material is, for example, a median diameter (D50) measured using a laser particle size distribution analyzer.

[0234] The negative electrode active material may include, for example, at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material. The carbon-based negative electrode active material may be, for example, amorphous carbon. Examples of the carbon-based negative electrode active material include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., and any material classified as amorphous carbon in the relevant technical field may be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. The metal or metalloid negative electrode active material includes, but is not limited to, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), and any metal or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used. For example, nickel (Ni) does not form an alloy with lithium, and therefore is not a metal negative electrode active material in the present specification. The negative electrode active material layer includes a type of negative electrode active material among these negative electrode active materials, or includes a mixture of a plurality of different negative electrode active materials. For example, the negative electrode active material layer may include a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture may be, for example, 10:1 to 1:2, 10:1 to 1:1, 7:1 to 1:1, 5:1 to 1:1, or 4:1 to 2:1 by weight.The negative electrode active material included in the negative electrode active material layer may include a mixture of first particles made of, for example, amorphous carbon and second particles made of a metal or a metalloid. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The content of the second particles is 8 to 60 wt%, 10 to 50 wt%, 15 to 40 wt%, or 20 to 30 wt% based on the total weight of the mixture. When the second particles have a content in this range, the cycle characteristics of, for example, a lithium secondary battery are further improved.

[0235] The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders. When the negative electrode active material layer does not include a binder, the negative electrode active material layer can be easily separated from the ceramic coating layer (21) or the negative electrode current collector (21). The content of the binder included in the negative electrode active material layer may be, for example, 1 to 20 wt% based on the total weight of the negative electrode active material layer.

[0236] The thickness of the negative electrode active material layer may be, for example, 0.1 ㎛ to 500 ㎛, or 100 ㎛ to 50 ㎛. The thickness of the negative electrode active material layer may be, for example, 1% to 50%, 1% to 30%, 1% to 10%, or 1% to 5% of the thickness of the positive electrode active material layer. If the thickness of the negative electrode active material layer is too thin, lithium dendrites formed between the negative electrode active material layer and the negative electrode current collector may collapse the negative electrode active material layer, making it difficult to improve the cycle characteristics of the lithium secondary battery. If the thickness of the negative electrode active material layer increases excessively, the energy density of the lithium secondary battery employing the negative electrode (20) may decrease, and it may be difficult to improve the cycle characteristics.

[0237] When the thickness of the negative electrode active material layer decreases, for example, the charge capacity of the negative electrode active material layer also decreases. The charge capacity of the negative electrode active material layer may be, for example, 0.1% to 50%, 1% to 30%, 1% to 10%, 1% to 5%, or 1% to 2% of the charge capacity. If the charge capacity of the negative electrode active material layer is too small, lithium dendrites formed between the negative electrode active material layer and the negative electrode current collector may collapse the negative electrode active material layer, making it difficult to improve the cycle characteristics of the lithium secondary battery. If the charge capacity of the negative electrode active material layer increases excessively, the energy density of the lithium secondary battery using the negative electrode (20) may decrease, and it may be difficult to improve the cycle characteristics. The charge capacity of the positive electrode active material layer is obtained by multiplying the charge capacity density (mAh / g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer. When multiple types of positive electrode active materials are used, the charge capacity density Х mass value is calculated for each positive electrode active material, and the sum of these values ​​is the charge capacity of the positive electrode active material layer. The charge capacity of the negative electrode active material layer is also calculated in the same way. That is, the charge capacity of the negative electrode active material layer is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the negative electrode active material layer. When multiple types of negative electrode active materials are used, the charge capacity density Х mass value is calculated for each negative electrode active material, and the sum of these values ​​is the capacity of the negative electrode active material layer. Here, the charge capacity density of the positive electrode active material and the negative electrode active material is the estimated capacity using an all-solid-state half-cell using lithium metal as a counter electrode. The charge capacity of the positive electrode active material layer and the negative electrode active material layer are directly measured by measuring the charge capacity using an all-solid-state half-cell. The charge capacity density is obtained by dividing the measured charge capacity by the mass of each active material. Alternatively, the charge capacity of the positive electrode active material layer and the negative electrode active material layer may be the initial charge capacity measured at the first charge cycle.

[0238] [Lithium secondary battery]

[0239] According to one embodiment, a lithium secondary battery includes a positive electrode; a negative electrode; and an electrolyte disposed between the positive electrode and the negative electrode. The lithium secondary battery may further include a separator. Such a lithium secondary battery can simultaneously provide excellent life characteristics. The lithium secondary battery may be, but is not limited to, a lithium primary battery, a lithium secondary battery, a lithium-sulfur battery, a lithium-air battery, etc., and any lithium secondary battery used in the relevant technical field may be used.

[0240] Lithium secondary batteries are manufactured by, for example, the following exemplary methods, but are not necessarily limited to these methods and are adjusted according to required conditions.

[0241] (anode)

[0242] First, a positive electrode active material composition is prepared by mixing a positive electrode active material, a conductive agent, a binder, and a solvent. The prepared positive electrode active material composition is directly coated on an aluminum current collector and dried to produce a positive electrode plate having a positive electrode active material layer formed thereon. Alternatively, the positive electrode active material composition is cast on a separate support, and then the film obtained by peeling from the support is laminated on the aluminum current collector to produce a positive electrode plate having a positive electrode active material layer formed thereon.

[0243] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0244] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0245] As an example, a compound represented by any one of the following chemical formulas may be used: Lia A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mr 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mr b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mr 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mr 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0246] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0247] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less, based on 100 mol% of metals excluding lithium in the lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0248] The cathode active material is, for example, Li a Ni x Co y M z O 2-b A b (1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0 <y≤0.3, 0<z≤0.3, 및 x+y+z=1이고, M은 망간(Mn), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합), LiNi x Co y Mn z O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1), LiNi x Co y Al z O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1), LiNix Co y Mn z Al w O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1), Li a Co x M y O 2-b A b (1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, and A is F, S, Cl, Br or a combination thereof), Li a Ni x Mn y M' z O 2-b A b (1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고, M'는 코발트(Co), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합), Li a M1 x M2 y PO 4-b X b(Here, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며, M1이 크롬(Cr), 망간(Mn), 철(Fe), 코발트(Co), 니켈(Ni), 구리(Cu), 지르코늄(Zr) 또는 이들의 조합이며, M2가 마그네슘(Mg), 칼슘(Ca), 스트론튬(Sr), 바륨(Ba), 티탄(Ti), 아연(Zn), 보론(B), 니오븀(Nb), 갈륨(Ga), 인듐(In), 몰리브덴(Mo), 텅스텐(W), 알루미늄(Al), 실리콘(Si), 크롬(Cr), 바나듐(V), 스칸듐(Sc), 이트륨(Y) 또는 이들의 조합이며, X가 O, F, S, P 또는 이들의 조합), Li a M3 z PO4 (0.90≤a≤1.1, 0.9≤z≤1.1, and M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof).

[0249] The conductive material may include, but is not limited to, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. Any conductive material used in the relevant technical field may be used. Alternatively, the anode may not include a separate conductive material, for example.

[0250] As binders, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the above-mentioned polymers, styrene butadiene rubber-based polymers, etc. are used, and as solvents, N-methylpyrrolidone (NMP), acetone, water, etc. are used, but are not necessarily limited to these, and any solvent used in the relevant technical field may be used.

[0251] A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material and may further include a binder and / or a conductive material.

[0252] For example, the anode may further include an additive that can act as a sacrificial anode.

[0253] The content of the positive electrode active material may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive electrode active material layer, and the contents of the binder and conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0254] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0255] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0256] The positive electrode collector uses a plate or foil made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The thickness of the positive electrode collector is, for example, 1 ㎛ to 100 ㎛, 1 ㎛ to 50 ㎛, 5 ㎛ to 25 ㎛, or 10 ㎛ to 20 ㎛.

[0257] The cathode current collector may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. The metal layer can act as an electrochemical fuse and cut off in case of overcurrent to prevent short circuits. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. As the thickness of the metal layer decreases, the limit current and / or maximum current of the positive electrode current collector decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added to the metal layer for external connection. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melt, so that the metal layer can be electrically connected to the lead tab. To strengthen the welding between the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure as the cathode current collector, the weight of the cathode can be reduced, and as a result, the energy density of the cathode and lithium battery can be improved.

[0258] (electrolyte)

[0259] Next, an electrolyte is prepared. The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof. The electrolyte is, for example, an organic electrolyte. The liquid electrolyte is as mentioned in the liquid electrolyte of the gel polymer electrolyte.

[0260] The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0261] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La yTiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, x is an integer from 1 to 10) is one or more selected from. The solid electrolyte is manufactured by a sintering method, etc. For example, the oxide-based solid electrolyte is Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 A garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10).

[0262] The sulfide-based solid electrolyte may include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof. The sulfide-based solid electrolyte particles may include Li2S, P2S5, SiS2, GeS2, B2S3, or a combination thereof. The sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles are known to have high lithium ion conductivity compared to other inorganic compounds. For example, the sulfide-based solid electrolyte includes Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte includes Li2S-P2S5, the mixing molar ratio of Li2S to P2S5 may be, for example, in a range of about 50:50 to about 90:10. In addition, Li3PO4, halogen, halogen compound, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x( "LIPON", 0 <x<4, 0<y<3), Li 3.25 Ge 0.25 P 0.75S4("ThioLISICON"), Li2O-Al2O3-TiO2-P2O 5( An inorganic solid electrolyte prepared by adding "LATP") etc. to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5; Li2S-P2S5-LiX (X=halogen element); Li2S-P2S5-Li2O; Li2S-P2S5-Li2O-LiI; Li2S-SiS2; Li2S-SiS2-LiI; Li2S-SiS2-LiBr; Li2S-SiS2-LiCl; Li2S-SiS2-B2S3-LiI; Li2S-SiS2-P2S5-LiI; Li2S-B2S3; Li2S -P2S5-Z m S n (0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga); Li2S-GeS2; Li2S-SiS2-Li3PO4; 및 Li2S-SiS2-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다. 또한, 소성(calcinations) 공정이 상기 처리 후에 수행될 수 있다. 황화물계 고체전해질은 비정질이거나, 결정질이거나, 이들이 혼합된 상태일 수 있다.

[0263] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or a polymer having ion-conducting functional groups. The polymer solid electrolyte may be, for example, a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may not, for example, comprise a liquid.

[0264] The polymer solid electrolyte comprises a polymer, and the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), Polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi) +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more or 1,000,000 Dalton or more.

[0265] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0266] A polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The polymer gel electrolyte may be, for example, a polymer electrolyte that is in a gel state at 25°C and 1 atm. The polymer gel electrolyte may, for example, have a gel state without containing a liquid. The liquid electrolyte used in the polymer gel electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature, is composed solely of ions, and is liquid at room temperature or a molten salt at room temperature. The ionic liquid comprises, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N- It may include at least one selected from compounds containing at least one anion selected from. The polymer solid electrolyte may form a polymer gel electrolyte by being impregnated in a liquid electrolyte, for example, in a secondary battery. The polymer gel electrolyte may further include inorganic particles. The polymer included in the polymer gel electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer gel electrolyte may be, for example, 500 Dalton or more, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0267] (cathode)

[0268] The cathode contains a cathode current collector.

[0269] Although not shown in the drawing, the negative electrode current collector (21) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The metal layer may correspond to, for example, the first metal substrate. The metal layer may additionally include a coating layer including a second metal. The negative electrode current collector (21) may additionally include a metal piece and / or a lead tab. For more specific details on the base film, metal layer, metal chip, and lead tab of the negative electrode current collector (21), refer to the positive electrode current collector. By having such a structure, the negative electrode current collector (21) can reduce the weight of the negative electrode, thereby improving the energy density of the negative electrode and the lithium battery.

[0270] A negative electrode active material layer may be formed on the negative electrode current collector. The negative electrode active material layer may be formed as a lithium deposition layer after charging. Alternatively, the negative electrode active material layer may be formed using a negative electrode active material during battery assembly.

[0271] The method of forming a negative electrode active material layer using a negative electrode active material can be manufactured in the same manner as described above, except that the negative electrode active material is used instead of the positive electrode active material when forming the positive electrode active material layer.

[0272] A lithium secondary battery may further include, for example, a thin film comprising an element capable of forming an alloy with lithium on one surface of an anode current collector. The thin film is disposed between the anode current collector and the anode active material layer. The thin film includes, for example, an element capable of forming an alloy with lithium. Elements capable of forming an alloy with lithium include, but are not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film may be composed of one of these metals or an alloy of several types of metals. By disposing the thin film on one surface of the anode current collector, for example, the deposition shape of the first anode active material layer deposited between the thin film and the anode active material layer becomes flatter, and the cycle characteristics of the lithium secondary battery may be further improved.

[0273] (Separator)

[0274] A separator may be further placed between the anode and cathode.

[0275] Any separator commonly used in lithium secondary batteries can be used.

[0276] As such a separator, a multilayer membrane of two or more layers of polyethylene, polypropylene, polyvinylidene fluoride, or these may be used, and of course, a mixed multilayer membrane such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0277] The above separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0278] The above porous substrate may be a polymer film formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyarylether ketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene, or a copolymer or mixture of two or more thereof.

[0279] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0280] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include inorganic particles selected from, but not limited to, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0281] The organic and inorganic substances may be mixed and present in one coating layer, or a coating layer including an organic substance and a coating layer including an inorganic substance may be present in a laminated form.

[0282] A lithium secondary battery according to an embodiment may further include a solid electrolyte. The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a combination thereof.

[0283] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), Li3PO4, Li x Ti y(PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, x is an integer from 1 to 10) is one or more selected from. The solid electrolyte is manufactured by a sintering method, etc. For example, the oxide-based solid electrolyte is Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 A garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10).

[0284] The sulfide-based solid electrolyte may include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof. The sulfide-based solid electrolyte particles may include Li2S, P2S5, SiS2, GeS2, B2S3, or a combination thereof. The sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles are known to have high lithium ion conductivity compared to other inorganic compounds. For example, the sulfide-based solid electrolyte includes Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte includes Li2S-P2S5, the mixing molar ratio of Li2S to P2S5 may be, for example, in a range of about 50:50 to about 90:10. In addition, Li3PO4, halogen, halogen compound, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x( "LIPON", 0 <x<4, 0<y<3), Li 3.25 Ge 0.25 P 0.75 S4("ThioLISICON"), Li2O-Al2O3-TiO2-P2O 5( An inorganic solid electrolyte prepared by adding "LATP") etc. to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5; Li2S-P2S5-LiX (X=halogen element); Li2S-P2S5-Li2O; Li2S-P2S5-Li2O-LiI; Li2S-SiS2; Li2S-SiS2-LiI; Li2S-SiS2-LiBr; Li2S-SiS2-LiCl; Li2S-SiS2-B2S3-LiI; Li2S-SiS2-P2S5-LiI; Li2S-B2S3; Li2S -P2S5-Z m S n(0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga); Li2S-GeS2; Li2S-SiS2-Li3PO4; 및 Li2S-SiS2-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다. 또한, 소성(calcinations) 공정이 상기 처리 후에 수행될 수 있다. 황화물계 고체전해질은 비정질이거나, 결정질이거나, 이들이 혼합된 상태일 수 있다.

[0285] (lithium secondary battery)

[0286] Referring to FIG. 4, a lithium secondary battery (1) according to an embodiment includes a positive electrode (3), the above-described negative electrode (2), and a separator (4). A gel-type polymer electrolyte (not shown) may be disposed between the electrolyte and the positive electrode. The positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). An organic electrolyte is injected into the battery case (5) and sealed with a cap assembly (6), thereby completing the lithium secondary battery (1). The battery case (5) is cylindrical, but is not necessarily limited to this shape, and may be, for example, square, thin-film, etc.

[0287] Referring to FIG. 5, a lithium secondary battery (1) according to an embodiment includes a positive electrode (3), a negative electrode (2), and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), and the positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). An electrode tab (8) that serves as an electrical path for guiding the current formed in the battery structure (7) to the outside may be included. An organic electrolyte is injected into the battery case (5) and sealed to complete the lithium secondary battery (1). The battery case (5) is not necessarily limited to a square shape, and may be, for example, a cylindrical shape, a thin film shape, etc.

[0288] Referring to FIG. 6, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2) according to one embodiment, and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), thereby forming a battery structure. A gel-type polymer electrolyte between the separator and the positive electrode is not shown. A battery structure (7) is stacked in a bi-cell structure and then accommodated in a battery case (5). An electrode tab (8) that serves as an electrical path for guiding the current formed in the battery structure (7) to the outside may be included. An organic electrolyte is injected into the battery case (5) and sealed, thereby completing the lithium secondary battery (1). The battery case (5) is not necessarily limited to a square shape, but may be, for example, a cylindrical shape, a thin-film shape, etc.

[0289] A pouch-type lithium secondary battery corresponds to the lithium secondary batteries of FIGS. 5 and 6, each of which uses a pouch as a battery case. The pouch-type lithium secondary battery includes one or more battery structures. An electrolyte is disposed between a positive electrode and a negative electrode, or an electrolyte and a separator are disposed to form a battery structure. The battery structures are laminated in a bi-cell structure, then impregnated with a liquid electrolyte, and accommodated and sealed in a pouch, thereby completing a pouch-type lithium secondary battery. For example, although not shown in the drawings, the above-described positive electrode, negative electrode, and separator may be simply laminated and accommodated in a pouch in the form of an electrode assembly, or may be wound or folded into a jellyroll-shaped electrode assembly and then accommodated in a pouch. Subsequently, an organic electrolyte is injected into the pouch and sealed, thereby completing a lithium secondary battery.

[0290] The lithium secondary battery of the present disclosure has excellent discharge capacity and lifespan characteristics, as well as high energy density, and is therefore used in, for example, electric vehicles (EVs). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). It is also used in applications requiring large amounts of power storage, such as electric bicycles and power tools.

[0291] Lithium secondary batteries are stacked to form a battery module, and the battery modules form a battery pack. Such a battery pack can be used in any device requiring high capacity and high output, such as laptops, smartphones, and electric vehicles. A battery module includes, for example, a plurality of batteries and a frame that holds them. A battery pack includes, for example, a plurality of battery modules and a bus bar that connects them. The battery module and / or the battery pack may further include a cooling device. The plurality of battery packs are controlled by a battery management system. The battery management system includes a battery pack and a battery control device connected to the battery pack.

[0292] [Method for manufacturing lithium secondary batteries]

[0293] A lithium secondary battery according to an embodiment can be manufactured through the steps of: preparing an anode current collector; preparing a separator; preparing a cathode; preparing a battery assembly by laminating the anode current collector, separator, and cathode; injecting a composition for forming a gel polymer electrolyte, which includes a crosslinking monomer for forming a gel polymer and a liquid electrolyte, into the battery assembly; and performing a heat treatment to form a gel polymer electrolyte.

[0294] In a lithium secondary battery according to an embodiment, a separator containing a gel polymer electrolyte can be formed in situ by injecting a composition for forming a gel polymer electrolyte into a battery assembly as described above and heat-treating the composition. Alternatively, a separator containing a gel polymer electrolyte can be manufactured separately to form a self-supporting film, which is then placed on a negative electrode current collector and a positive electrode placed on top of the self-supporting film, thereby manufacturing a lithium secondary battery.

[0295] The above lithium secondary battery may further include a separator.

[0296] The separator may contain a gel polymer electrolyte. The separator may further contain a liquid electrolyte.

[0297] A step of forming a protective film on the negative electrode current collector may be further included.

[0298] The step of forming the protective film may be performed by coating and heat-treating a composition for forming a protective film, which includes at least one binder selected from a binder precursor and a binder and boron nitride, on a negative electrode current collector. Here, the binder precursor may include, for example, a first polymer and a second polymer, and the binder refers to the binder mentioned in the above-described protective film.

[0299] A solvent such as N-methylpyrrolidone or dimethylformamide may be added to the composition for forming the protective film. The content of the solvent may be 0.05 to 5 parts by weight based on 100 parts by weight of the total weight of boron nitride and binder.

[0300] The above protective film may further include a lithium salt. The content of the lithium salt is 30 to 80 parts by weight, 40 to 60 parts by weight, or 45 to 55 parts by weight based on 100 parts by weight of the total weight of the binder and the lithium salt.

[0301] The composition for forming a protective film may further include a second polymer having a crosslinkable functional group with the first polymer containing a hydroxyl group. The protective film formed from the composition for forming a protective film further includes a crosslinked polymer of the first polymer and the second polymer. Here, the mixing weight ratio of the first polymer containing a hydroxyl group and the second polymer is adjusted to be in the range of 50:50 to 99:1, 50:50 to 99:1, or 60:40 to 90:10.

[0302] The above second polymer is at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0303] When the second polymer is a fluorinated polyamic acid having a carboxyl group, a composition for forming a protective film containing the same may be coated on a negative electrode current collector and dried, and then further heat treatment may be performed to cause a crosslinking reaction between the first polymer and the second polymer to form a protective film containing a crosslinked polymer. The heat treatment may vary depending on the composition of the first polymer and the second polymer, but may be performed at, for example, 80 to 200°C, 100 to 200°C, 150 to 200°C, or 150 to 190°C. When the heat treatment temperature is within the above range, the protective film formed on the electrode surface can minimize exposure of the electrolyte at the electrode surface and create a uniform lithium ion flow throughout the electrode, thereby effectively suppressing lithium dendrite growth.

[0304] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0305] (Manufacture of gel polymer electrolyte and lithium secondary battery)

[0306] Example 1: Negative electrode current collector / separator + GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) / positive electrode

[0307] A copper foil with a thickness of 10 μm was prepared as a negative current collector.

[0308] A polyethylene single film having a thickness of 20 μm was laminated as a separator on top of copper foil, and a positive electrode was laminated on the other side of the separator to manufacture a laminate. A composition for forming a gel polymer electrolyte was injected into the prepared laminate, and heat-treated at 70°C for 120 minutes to manufacture a lithium secondary battery in which a gel polymer electrolyte was formed in the pores of the separator. The lithium secondary battery had a structure of positive electrode / gel polymer electrolyte (separator) / protective film / negative electrode current collector. The content of the gel polymer in the gel polymer electrolyte was 4 parts by weight based on 100 parts by weight of the gel polymer electrolyte, and the content of the liquid electrolyte was 96 parts by weight.

[0309] The composition for forming the above gel polymer electrolyte was prepared by mixing dipentaerythritol hexaacrylate (DPHA), a 6-functional crosslinking agent that is a crosslinking monomer, Fluorolink AD1700 (MW: 1,500) from Solvay, and 240.30 g / mol of benzoin ethyl ether (Sigma-Aldrich) as a liquid electrolyte and initiator.

[0310] The composition for forming the above gel polymer electrolyte contained 4 parts by weight of a crosslinking monomer comprising DPHA and AD1700 in a weight ratio of 3:1, 96 parts by weight of a liquid electrolyte, and an initiator based on 100 parts by weight of the total weight of the composition. The initiator was used in an amount of 5 parts by weight based on 100 parts by weight of the crosslinking monomer.

[0311] <dpha>

[0312]

[0313] <AD 1700>

[0314]

[0315] The liquid electrolyte used was a 2:1 volume ratio mixed solvent of diethyl carbonate (DEC) and fluoroethylene carbonate (FEC), to which 0.6 M LiBF4 and 0.6 M LiDFOB (lithium difluoro(oxalate)borate) and acetonitrile were added. The content of acetonitrile in the liquid electrolyte was 8.74 wt% based on the total weight of the liquid electrolyte, and the content of FEC was 36.7 wt% based on the total weight of the liquid electrolyte.

[0316] The above anode was manufactured according to the following method.

[0317] Li 1.04 Ni 0.88 Co 0.1 Al 0.02 O2 powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to obtain a weight ratio of active material:carbon conductive material:binder = 90:5:5 to prepare a positive electrode active material slurry. The prepared slurry was coated on a 15 ㎛ thick aluminum substrate using a doctor blade, dried under reduced pressure at 120°C, and then rolled using a roll press to form a sheet to manufacture a positive electrode.

[0318] In the lithium secondary battery manufactured according to the above process, a lithium precipitation layer was formed between the negative electrode current collector and the separator.

[0319] Example 2: Negative electrode current collector / separator + GPE (gel polymer (DPHA / DRIC (3 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) / positive electrode

[0320] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that dipentaerythritol hexaacrylate (DPHA), a 6-functional crosslinking agent that is a crosslinking monomer, and Fluorolink AD1700 (MW: 1,500) from Solvay were used instead of DPHA and DRIC of the following compound 1.

[0321] Compound 1

[0322]

[0323] In chemical formula 1, n is 5, EG represents an ethylene group, DEG represents diethylene glycol, and TMP represents trimethylolpropane.

[0324] Example 3: GPE (gel polymer (DPHA / AD1700 (1 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4)

[0325] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the mixing weight ratio of DPHA and AD1700 was changed to 1:1 when manufacturing a composition for forming a gel polymer electrolyte.

[0326] Example 4: GPE (gel polymer (DPHA / DRIC (1 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4)

[0327] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 2, except that the mixing weight ratio of DPHA and DRIC was changed to 1:1 when manufacturing a composition for forming a gel polymer electrolyte.

[0328] Example 5: GPE (gel polymer (DPHA / AD1700 (3 / 1) 8%) + LE, LE (acetonitrile + LiDFOB + LiBF4)

[0329] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the total content of DPHA and AD1700 was changed to 8 wt% based on the total weight of the gel polymer electrolyte composition when manufacturing the composition for forming a gel polymer electrolyte.

[0330] Example 6: GPE (gel polymer (TMPTMA / AD1700 (3 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4)

[0331] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that TMPTMA was used instead of DPHA when manufacturing a composition for forming a gel polymer electrolyte.

[0332] Comparative Example 1: Negative electrode current collector / separator + GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE (LiDFOB + LiBF4, acetonitrile-free) / positive electrode

[0333] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that acetonitrile was not used in the preparation of the liquid electrolyte of the composition for forming a gel polymer electrolyte.

[0334] Comparative Example 2: Negative electrode current collector / separator + GPE (gel polymer (DPHA) 4%) + LE (LiDFOB + LiBF4, acetonitrile-free) / positive electrode

[0335] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that only DPHA was used instead of DPHA and AD1700 as crosslinking monomers when manufacturing a composition for forming a gel polymer electrolyte.

[0336] Comparative Example 3: Negative electrode current collector / separator + GPE (gel polymer (EG-DMA / AD1700 (3 / 1) 4%) 4%) + LE (acetonitrile + LiDFOB + LiBF4) / positive electrode

[0337] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that EG-DMA (ethyleneglycol dimethacrylate) and AD1700 were used instead of DPHA and AD1700 as crosslinking monomers when manufacturing a composition for forming a gel polymer electrolyte.

[0338] [EG-DMA, MW= 198.22]

[0339]

[0340] Comparative Example 4: Negative electrode current collector / separator + GPE (gel polymer (EG-DMA) 4%) + LE (acetonitrile + LiDFOB + LiBF4) / positive electrode

[0341] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that EG-DMA (ethyleneglycol dimethacrylate) was used instead of DPHA and AD1700 as a crosslinking monomer when manufacturing a composition for forming a gel polymer electrolyte.

[0342] Comparative Example 5: Negative electrode current collector / separator + GPE (gel polymer (AD1700) 4%) + LE (acetonitrile + LiDFOB + LiBF4) / positive electrode

[0343] A gel polymer electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that AD1700 was used instead of DPHA and AD1700 as a crosslinking monomer when manufacturing a composition for forming a gel polymer electrolyte.

[0344] Evaluation Example 1: High Temperature (45℃) Lifespan

[0345] The charge / discharge characteristics of the lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5 were evaluated under the following conditions.

[0346] The battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) during discharge (formation cycle).

[0347] A lithium secondary battery that had undergone a Mars cycle was charged at a constant current of 0.2 C at 45°C until the voltage reached 4.3 V (vs. Li). Subsequently, the battery was cut off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C until the voltage reached 3.6 V (vs. Li) (1st cycle). This cycle was repeated under the same conditions until the 160th cycle.

[0348] In all charge / discharge cycles, a 10-minute pause was provided after each charge / discharge cycle. Some of the results of the high-temperature charge / discharge experiments are shown in Table 1.

[0349] Distinction condition Cycle number (n) @ 80% Example 1 GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 231 Example 2 GPE (gel polymer (DPHA / DRIC (3 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 229 Example 3 GPE (gel polymer (DPHA / AD1700 (1 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 223 Example 4 GPE (gel polymer (DPHA / DRIC (1 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 219 Example 5GPE(Gel polymer(DPHA / AD1700(3 / 1) 8%)+LE, LE(Acetonitrile+LiDFOB+LiBF4)206Example 6GPE(Gel polymer(TMPTMA / AD1700(3 / 1) 4%)+LE, LE(Acetonitrile+LiDFOB+LiBF4)184Comparative Example 1GPE(Gel polymer(DPHA / AD1700(3 / 1) 4%)+LE(LiDFOB+LiBF4, Acetonitrile-free)120Comparative Example 2GPE(Gel polymer(DPHA) 4%)+LE(LiDFOB+LiBF4, Acetonitrile-free)125Comparative Example 3GPE(Gel polymer(EG-DMA / AD1700(3 / 1) 4%)+LE, LE(Acetonitrile+LiDFOB+LiBF4)145Comparative Example 4GPE(Gel polymer(EG-DMA) 4%)+LE, LE(Acetonitrile+LiDFOB+LiBF4)53Comparative Example 5GPE(Gel polymer(AD1700) 4%)+LE, LE(Acetonitrile+LiDFOB+LiBF4)Gel not formed

[0350] Evaluation Example 2: High-rate characteristics

[0351] The lithium secondary batteries manufactured in Examples 1 to 6 and Comparative Examples 1 to 4 were charged at a constant current of 0.1 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the batteries were discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) during discharge (formation cycle).

[0352] The lithium secondary battery that had undergone the Mars cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.2 C rate until the voltage reached 3.6 V (vs. Li), and the same method was used for 4 charge / discharge cycles, for a total of 5 discharge cycles at 0.2 C rate, and the third discharge cycle was used as the result (1 st cycle).

[0353] 1 st Cycle 3 rd The cycle was repeated under the same conditions.

[0354] 3 rd The cycled lithium battery was charged at a constant current of 0.2 C at 45°C until the voltage reached 4.3 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C until the voltage reached 2.8 V (vs. Li) (4 th cycle).

[0355] 4 th Cycle 8 th The cycle was repeated under the same conditions.

[0356] 8 th The cycled lithium battery was charged at a constant current of 0.33 C at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 1 C until the voltage reached 2.8 V (vs. Li) (9 th cycle).

[0357] 9 th Cycle 13 th The cycle was repeated under the same conditions.

[0358] 13 th The cycled lithium battery was charged at a constant current of 0.33 C at 45°C until the voltage reached 4.3 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 2 C until the voltage reached 2.8 V (vs. Li) (14 th cycle).

[0359] 14 th Cycle 18 th The cycle was repeated under the same conditions.

[0360] 18 th The cycled lithium battery was charged at a constant current of 0.33 C at 45°C until the voltage reached 4.3 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 3 C until the voltage reached 2.8 V (vs. Li) (19 th cycle).

[0361] 19 th Cycle 23 th The cycle was repeated under the same conditions.

[0362] 23 th The cycled lithium battery was charged at a constant current of 0.33 C at 45°C until the voltage reached 4.3 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.2 C until the voltage reached 2.8 V (vs. Li) (24 th cycle).

[0363] 24 th The cycled lithium battery was charged at a constant current of 0.33 C at 45°C until the voltage reached 4.3 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C until the voltage reached 2.8 V (vs. Li) (25 th cycle).

[0364] 25 th Cycle 30 th The cycle was repeated under the same conditions.

[0365] In all the above charge / discharge cycles, a pause of 10 minutes was allowed after each charge / discharge cycle.

[0366] Some of the results of the above charge-discharge experiment are shown in Table 2 below.

[0367] The high-rate characteristic is defined by Equation 3 below.

[0368] <Formula 2>

[0369] High rate characteristics [%] = [3C rate discharge capacity / 0.2C rate discharge capacity)] Х 100

[0370] Classification conditions High yield characteristics (%) Example 1 GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 47.2 Example 2 GPE (gel polymer (DPHA / DRIC (3 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 44.2 Example 3 GPE (gel polymer (DPHA / AD1700 (1 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 46.8 Example 4 GPE (gel polymer (DPHA / DRIC (1 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 44.0 Example 5GPE(Gel polymer(DPHA / AD1700(3 / 1) 8%)+ LE, LE(Acetonitrile+ LiDFOB+LiBF4)46.6Example 6GPE(Gel polymer(TMPTMA / AD1700(3 / 1) 4%)+ LE, LE(Acetonitrile+ LiDFOB+LiBF4)42.9Comparative Example 1GPE(Gel polymer(DPHA / AD1700(3 / 1) 4%)+ LE(LiDFOB+LiBF4, Acetonitrile-free)32.2Comparative Example 2GPE(Gel polymer(DPHA) 4%)+ LE(LiDFOB+LiBF4, Acetonitrile-free)31.9Comparative Example 3GPE(Gel polymer(EG-DMA) 4%)+ LE, LE(Acetonitrile+ LiDFOB+ LiBF4)35.7Comparative example 4GPE (gel polymer (EG-DMA) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4)35.5

[0371] In the lithium secondary batteries of Examples 1 to 6, when more anions interact with the polymer chain, t+ increases and the binding energy decreases when Li moves between O (oxygen) in the chain, allowing rapid movement of Li ions and thereby improving the rate characteristics.

[0372] Evaluation Example 3: Ionic Conductivity

[0373] The ionic conductivity of the gel polymer electrolyte in the lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 4 was investigated and is shown in Table 3 below. The ionic conductivity was measured by applying a voltage bias of 10 mV to the gel polymer electrolyte in the frequency range of 1 Hz to 1 MHz, scanning the temperature, and measuring the resistance.

[0374] Classification conditionsRoom temperature ionic conductivity (mS / cm)High temperature ionic conductivity (mS / cm)Example 1GPE(Gel polymer(DPHA / AD1700(3 / 1) 4%)+LE, LE(Acetonitrile+LiDFOB+LiBF4)0.430.61Example 2GPE(Gel polymer(DPHA / DRIC(3 / 1) 4%)+LE, LE(Acetonitrile+LiDFOB+LiBF4)0.390.56Example 3GPE(Gel polymer(DPHA / AD1700(1 / 1) 4%)+LE, LE(Acetonitrile+LiDFOB+LiBF4)0.420.59Example 4GPE(Gel polymer(DPHA / DRIC(1 / 1) 4%)+LE, LE(Acetonitrile+ LiDFOB + LiBF4) 0.38 0.56 Example 5 GPE (gel polymer (DPHA / AD1700 (3 / 1) 8%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 0.42 0.61 Example 6 GPE (gel polymer (TMPTMA / AD1700 (3 / 1) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 0.36 0.53 Comparative Example 1 GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE (LiDFOB + LiBF4, acetonitrile free) 0.31 0.46 Comparative Example 2 GPE (gel polymer (DPHA) 4%) + LE (LiDFOB + LiBF4, acetonitrile Free) 0.31 0.44 Comparative example 3 GPE (gel polymer (EG-DMA) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 0.26 0.37 Comparative example 4 GPE (gel polymer (EG-DMA) 4%) + LE, LE (acetonitrile + LiDFOB + LiBF4) 0.25 0.37

[0375] As shown in Table 3, it was found that the gel polymer electrolytes of Examples 1 to 6 had higher ionic conductivity at room temperature and high temperature compared to the gel polymer electrolytes of Comparative Examples 1 to 4.

[0376] Evaluation Example 4: Scanning Electron Microscopy Analysis

[0377] Scanning electron microscopy analysis was performed on the gel polymer electrolytes manufactured according to Example 1 and Comparative Example 1. The results of the scanning electron microscopy analysis are shown in Figs. 7 and 8.

[0378] Referring to FIG. 7, the gel polymer electrolyte of Example 1 contained acetonitrile, so that lithium transfer occurred only through the polymer chain, enabling a more uniform lithium supply than the gel polymer electrolyte of Comparative Example 1 of FIG. 8.

[0379] While exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is self-evident that those skilled in the art to which the present invention pertains can devise various modifications or variations within the scope of the technical concepts described in the patent claims, and these also naturally fall within the technical scope of the present invention.

[0380] [Explanation of symbols]

[0381] 1 Lithium secondary battery 2, 20 cathode

[0382] 3, 10 anode 4 separator

[0383] 5 Battery case 6 Cap assembly

[0384] 7 Battery structure 8 Electrode tab< / dpha>

Claims

1. A gel polymer electrolyte for a lithium secondary battery comprising a gel polymer and a liquid electrolyte. The above gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) A crosslinked product of a first polymerizable monomer which is a multifunctional acrylic monomer having three or more polymerizable functional groups and a second polymerizable monomer which is at least one selected from among a urethane acrylic monomer having two or more polymerizable functional groups and a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups; The above liquid electrolyte is a gel polymer electrolyte for a lithium secondary battery containing a lithium salt, an organic solvent, and acetonitrile.

2. In paragraph 1, A gel polymer electrolyte for a lithium secondary battery, wherein the content of the above acetonitrile is 2 to 30 wt% based on 100 wt% of the total weight of the liquid electrolyte.

3. In paragraph 1, A gel polymer electrolyte for a lithium secondary battery, wherein the concentration of the lithium salt is 0.1 M to 5 M.

4. In paragraph 1, The above lithium salt is a gel polymer electrolyte for a lithium secondary battery, comprising lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF4).

5. In paragraph 4, A gel polymer electrolyte for a lithium secondary battery, wherein the mixing weight ratio of lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF4) is 1:2 to 1:0.

3.

6. In paragraph 1, The above organic solvent contains a carbonate compound, A gel polymer electrolyte for a lithium secondary battery, wherein the carbonate compound comprises fluoroethylene carbonate (FEC) and diethyl carbonate (DEC).

7. In paragraph 6, A gel polymer electrolyte for a lithium secondary battery, wherein the mixing weight ratio of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) among the above carbonate compounds is 1:10 to 1:

1.

8. In paragraph 1, The multifunctional acrylic monomer having three or more polymerizable functional groups is pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate (TMPTMA), propoxylated (3) trimethylolpropane triacrylate (PO(3)TMPTA), propoxylated (6) trimethylolpropane triacrylate (PO(6)TMPTA), ethoxylated trimethylolpropane triacrylate, di(trimethylolpropane) tetraacrylate (Di(trimethylolpropane) tetraacrylate), pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), dipentaerythritol A gel polymer electrolyte for a lithium secondary battery, comprising dimethyl ether pentaacrylate (DPEPA), dipentaerythritol hexaacrylate (DPHA), or a combination thereof.

9. In paragraph 1, The urethane acrylic monomer having two or more functional groups includes two or more units represented by the following chemical formula 1, A gel polymer electrolyte for a lithium secondary battery, wherein the polymerizable monomer containing the perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups comprises a unit represented by the following chemical formula 2 and three or more units represented by the following chemical formula 3: <Chemical Formula 1> In the above chemical formula 1, * is a bonding site with an adjacent atom, <Chemical Formula 2> In chemical formula 2, * and *' are the bonding sites with adjacent atoms, respectively, m and n are greater than 0, and the sum of m+n is in the range of 2 to 300, <Chemical Formula 3> In the above chemical formula 3, R1 is hydrogen or a C1-C6 alkyl group, * is a bonding site with an adjacent atom.

10. In paragraph 1, The content of the above liquid electrolyte is 88 to 99 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte, A gel polymer electrolyte for a lithium secondary battery, wherein the gel polymer content is 1 to 12 parts by weight.

11. In a lithium secondary battery including a negative electrode current collector, a positive electrode, and an electrolyte disposed between the positive electrode and the negative electrode, A lithium secondary battery comprising the gel polymer electrolyte of any one of claims 1 to 10.

12. In paragraph 10, A lithium secondary battery further comprising a lithium metal layer disposed on the negative electrode current collector.

13. In paragraph 12, A lithium secondary battery, wherein the lithium metal layer comprises lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, or a combination thereof.

14. In the 13th paragraph, the lithium alloy contains lithium and a first metal, A lithium secondary battery, wherein the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

15. In paragraph 10, The above lithium secondary battery is a lithium secondary battery further including a separator.

16. A lithium secondary battery comprising a negative electrode active material layer between the negative electrode current collector and the electrolyte in the 10th paragraph.

17. A lithium secondary battery according to claim 16, wherein the negative active material layer comprises a carbon-based compound; a mixture of at least one selected from a carbon-based material and a first metal; a composite of at least one selected from a carbon-based material and a first metal; or a combination thereof.

18. In paragraph 17, The above carbon-based material includes amorphous carbon, The average particle diameter of the above amorphous carbon is 10 nm to 100 nm, A lithium secondary battery wherein the carbon-based material comprises carbon black, carbon nanotubes, carbon nanofibers, fullerenes, activated carbon, carbon fibers, or a combination thereof.

19. In paragraph 17, A lithium secondary battery, wherein the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

20. In the 10th paragraph, the positive electrode includes a positive electrode current collector and a positive electrode active material layer, At least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, The above base film contains a polymer, The above polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, A lithium secondary battery, wherein the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

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